Direct combustion chamber fuel injection technology has been advanced for improving the thermal efficiency of internal combustion engines such as the venerable Diesel engine and for gasoline engines designed to achieve greater fuel efficiency. The most fuel efficient engine types rely upon direct injection of fuel into the combustion chamber to produce stratified-charge combustion.
Difficult problems that have prevented most of the 800 million engines now existing from benefitting from stratified charge technology include: expensive, high pressure fuel pumps and injectors with small orifices are required to deliver fuel at high pressure for purposes of producing required surface-to-volume ratios for clean burning; dry fuels cause such pumps and fuel injectors to fail prematurely; ignition of preferred clean fuels requires ionizing conditions in air-fuel mixtures to initiate combustion which has defeated attempts to utilize compression ignition or the combination of fuel injectors and spark plugs in separate locations of the combustion chamber; gaseous fuels require much larger passageways than liquid fuels for equal power ratings and have not been directly injected because of the bulky, high-inertia, slow-acting components required for conventional fuel pumps and injectors; and because the parasitic losses for pumping and metering clean fuels has been unacceptable.